1. Field of the Invention
The present invention relates to a technology of monitoring degree of consumption of consumable components in an image forming apparatus.
2. Description of the Related Art
An image forming apparatus such as a copying machine or a printer forms an image on an image forming medium such as a sheet of printing paper by using an image forming material such as toner or ink. Image forming apparatuses include consumable components such as a photosensitive member and toner. Use of a consumable component after its life is over can lead to degradation of the image quality. Japanese Patent Application Laid-open No. 2003-91218 discloses a technology to monitor the wear and tear of the consumable components in an image forming apparatus and use the data to suppress degradation of the image quality.
Concretely, for example, amount of toner consumption in an image forming apparatus is estimated, and based on the estimated amount the user of the image forming apparatus is notified whether it is necessary to refill toner in the toner container.
The amount of toner consumption can be estimated by detecting the amount of toner in the toner container by using a sensor, or can be estimated based on the number of times the process of image formation has been performed. The amount of toner consumption can also be estimated based on various image forming conditions such as the paper size on which an image to be formed or the resolution at which the image is to be formed.
The value of the amount of toner consumption is stored in a nonvolatile rewritable memory. However, if for some reason the power supply to the image forming apparatus is temporarily discontinued before a new value of the amount of toner consumption, that is, the value of the amount of toner consumption obtained during the latest process of image formation, is stored in the memory, then it becomes difficult to accurately monitor the amount of toner consumption upon power restoration. Thus, e.g., even if large amount of toner is consumed during the latest process of image formation, the user might not be notified that it is necessary to refill the toner before subsequent process of image formation.